U.S. patent application number 13/230117 was filed with the patent office on 2013-03-14 for bend-limited flexible optical interconnect device for signal distribution.
This patent application is currently assigned to TYCO ELECTRONICS CORPORATION. The applicant listed for this patent is James Joseph EBERLE, JR.. Invention is credited to James Joseph EBERLE, JR..
Application Number | 20130064495 13/230117 |
Document ID | / |
Family ID | 47829907 |
Filed Date | 2013-03-14 |
United States Patent
Application |
20130064495 |
Kind Code |
A1 |
EBERLE, JR.; James Joseph |
March 14, 2013 |
BEND-LIMITED FLEXIBLE OPTICAL INTERCONNECT DEVICE FOR SIGNAL
DISTRIBUTION
Abstract
The invention relates to a bend limiting structure for
preventing a flexible optical circuit from being bent too sharply.
More particularly, the invention involves adding a bend limiting
layer or layers to the flexible optical circuit and/or any housing
or other structure within which it is enclosed or to which it is
attached. The bend-limiting layer may comprise a plurality of
blocks arranged in a line or plane and joined by a flexible film
that is thinner than the blocks with the blocks positioned close
enough to each other so that, if that plane of blocks is bent a
predetermined amount, the edges of the blocks will interfere with
each other and prevent the plane from being bent any further. The
blocks may be resilient also to provide a less abrupt bend-limiting
stop.
Inventors: |
EBERLE, JR.; James Joseph;
(Hummelstown, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EBERLE, JR.; James Joseph |
Hummelstown |
PA |
US |
|
|
Assignee: |
TYCO ELECTRONICS
CORPORATION
Berwyn
PA
|
Family ID: |
47829907 |
Appl. No.: |
13/230117 |
Filed: |
September 12, 2011 |
Current U.S.
Class: |
385/14 |
Current CPC
Class: |
G02B 6/3608 20130101;
G02B 6/32 20130101 |
Class at
Publication: |
385/14 |
International
Class: |
G02B 6/125 20060101
G02B006/125 |
Claims
1. A device for interconnecting optical signals between at least
one first optical component and at least one second optical
component comprising: a flexible optical circuit substrate layer
having first and second, opposed major surfaces; a plurality of
optical fibers disposed on the substrate, each of the optical
fibers having a first end and a second end; a bend limiting layer
attached to the flexible optical circuit so as to bend with and
substantially identically to the flexible optical circuit
substrate, the bend limiting layer comprising a plurality of blocks
disposed relative to each other such that adjacent pairs of the
blocks contact each other when the bend limiting layer is bent a
predetermined amount thereby resisting further bending of the bend
limiting layer and the flexible optical circuit substrate.
2. The device of claim 1 wherein the bend limiting layer is
attached to the first major surface of the flexible optical circuit
substrate.
3. The device of claim 1 further comprising a housing within which
the flexible optical circuit substrate is disposed and wherein the
bend limiting layer is attached to the housing.
4. The device of claim 1 further comprising: at least a first
light-guiding, fiber termination optical element disposed on the
substrate adjacent the first ends of the optical fibers positioned
to couple light with the optical fibers; and at least a second
light-guiding, fiber termination optical element disposed on the
substrate adjacent the second ends of the optical fibers positioned
to couple light with the optical fibers.
5. The device of claim 1 wherein the light-guiding, fiber
termination optical elements are lenses.
6. The device of claim 1 wherein the flexible optical circuit
substrate comprises a laminate having first and second layers and
wherein the plurality of optical fibers are embedded between the
first and second layers.
7. The device of claim 1 wherein the bend limiting layer further
comprises a film interconnecting the blocks.
8. The device of claim 7 wherein the film is resiliently
stretchable.
9. The device of claim 7 wherein the blocks and the film of the
bend limiting layer are unitary.
10. The device of claim 7 wherein the blocks extend in only one
direction perpendicularly from a plane defined by the film.
11. The device of claim 1 wherein the bend limiting layer comprises
a first bend limiting layer disposed on the first major surface of
the flexible optical circuit substrate and a second bend limiting
layer disposed on the second major surface of the flexible optical
circuit substrate.
12. The device of claim 1 wherein the blocks are arranged in a two
dimensional planar array.
13. The device of claim 12 wherein the blocks are arranged in rows
and columns.
14. The device of claim 12 wherein the bend limiting layer provides
different bend limits in different orthogonal directions.
15. The device of claim 3 wherein the housing is flexible.
16. The device of claim 3 wherein the housing comprises first and
second housing parts hingedly connected to each other.
Description
FIELD OF THE INVENTION
[0001] The invention pertains to fiber optic connectivity for high
speed signal distribution. More particularly, the invention
pertains to methods and apparatus for bend limiting a flexible
optical interconnect device.
BACKGROUND OF THE INVENTION
[0002] Fiber optic breakout cassettes are merely one form of
passive optical interconnect device commonly used for distributing
signals between one or more transmit optical components and one or
more receive optical components (often in opposite directions
simultaneously).
[0003] Other common passive optical interconnect devices are
optical multiplexers and demultiplexers, which comprise a flexible
optical circuit, for distributing signals between one or more
single- or multi-fiber optical connectors on the one hand and one
or more single- or multi-fiber optical connectors on the other
hand. Other common forms of optical interconnect include simple
patch cables and optical splitters.
[0004] Flexible optical circuits are passive optical components
that comprise one or more (typically multiple) optical fibers
imbedded on a flexible substrate, such as a Mylar or other flexible
polymer substrate. Commonly, although not necessarily, one end-face
of each fiber is disposed adjacent one longitudinal end of the
flexible optical circuit substrate and the other end face of each
fiber is disposed adjacent the opposite longitudinal end of the
flexible optical circuit substrate. The fibers extend past the
longitudinal ends of the flexible optical circuit (commonly
referred to as pigtails) so that they can be terminated to optical
connectors, which can be coupled to fiber optic cables or other
fiber optic components through mating optical connectors.
[0005] Flexible optical circuits are known, and hence, will not be
described in detail. However, they essentially comprise one or more
fibers sandwiched between two flexible sheets of material, such as
Mylar.TM. or another polymer. An epoxy may be included between the
two sheets in order to make them adhere to each other. Alternately,
depending on the sheet material and other factors, the two sheets
may be heated above their melting point to heat weld them together
with the fibers embedded between the two sheets.
[0006] FIG. 1, for example, shows a flexible optical circuit 100
that might be used in an optical multiplexer/demultiplexer. This
flexible optical circuit 100 commonly is referred to as a shuffle.
FIG. 2 shows a complete optical multiplexer/demultiplexer 200
including the shuffle 100 and a housing 102. The top of the housing
is removed in FIG. 2 to allow viewing of the internal components of
the device 200. This particular optical multiplexer/demultiplexer
200 is intended to distribute signals between a set of eight
multi-fiber optical cables 201 on the right side of the figure,
each containing eight fibers (not shown), and another set of eight
optical cables 203 on the left side of the figure, each cable
containing eight fibers (not shown). More particularly, the cables
201 and 203 terminate to suitable optical connectors 207 and 209,
respectively, which engage with mating connectors 211, 213,
respectively, through adapters 215, 217 disposed in the housing
102. For each of the eight right-hand cables 201, the fibers 105
embedded in the shuffle 100 break out the eight signal paths and
distribute one each to each of the eight left-hand cables 203, and
vice versa.
[0007] Flexible optical circuits such as shuffle 100 of FIGS. 1 and
2 can be bent too sharply. Particularly, there are three concerns
with respect to bending flexible optical circuits too sharply.
First, the optical fibers 105 embedded within them can break if
bent too sharply. Secondly, even if the fibers do not break, too
sharp of a bend in a fiber can cause light to escape from the core
of the fiber, thus leading to signal loss. Finally, the flexible
optical circuit substrate usually is a laminate, and bending a
laminate too sharply can cause it to de-laminate.
SUMMARY OF THE INVENTION
[0008] The invention relates to a bend limiting structure for
preventing a flexible optical circuit from being bent too sharply.
More particularly, the invention involves adding a bend limiting
layer or layers to the flexible optical circuit and/or any housing
or other structure within which it is enclosed or to which it is
attached. The bend-limiting layer may comprise a plurality of
blocks arranged in a line or plane and joined by a flexible film
that is thinner than the blocks with the blocks positioned close
enough to each other so that, if that plane of blocks is bent a
predetermined amount, the edges of the blocks will interfere with
each other and prevent the plane from being bent any further. The
blocks may be resilient also to provide a less abrupt bend-limiting
stop.
DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a perspective view of a flexible optical circuit
of the prior art.
[0010] FIG. 2 shows an optical multiplexer/de multiplexer
incorporating the flexible optical circuit of FIG. 1.
[0011] FIG. 3 is a top perspective view of a lensed flexible
optical circuit in accordance with the principles of the present
invention.
[0012] FIG. 4 shows an optical cassette in accordance with the
principles of the present invention comprising a housing and
incorporating a flexible optical circuit of FIG. 3.
[0013] FIG. 5 shows another optical cassette housing for housing a
flexible optical circuit in accordance with the principles of the
present invention.
[0014] FIG. 6 shows yet another optical cassette housing for
housing a flexible optical circuit in accordance with the
principles of the present invention.
[0015] FIG. 7 is a bottom perspective view of a lensed flexible
optical circuit that can replace the flexible optical circuit and
internal connectors of FIG. 3.
[0016] FIG. 8A is a sectional side view of the lensed flexible
optical circuit of FIG. 3 through section 8A shown in FIG. 7.
[0017] FIG. 8B is a sectional side view of the lensed flexible
optical circuit of FIG. 3 through section 8B shown in FIG. 7.
[0018] FIG. 9 is a side view of the lensed flexible optical circuit
of FIGS. 3, 4, 5A, and 5B bent to its limit in one dimension.
[0019] FIG. 10 is a cross-sectional side view of a bend limiting
layer in accordance with an alternate embodiment of the
invention.
[0020] FIG. 11 shows the housing of FIG. 7 including a pair of bend
limiting layers in accordance with the principles of the present
invention.
DETAILED DESCRIPTION
[0021] U.S. patent application Ser. No. 13/230,094, filed Sep. 12,
2011 (attorney docket number applicant NT-00354: undersigned
counsel docket number 357180.00284), which is incorporated herein
fully by reference, discloses a lensed flexible optical circuit
bearing at least one, but, more effectively, many optical fibers
embedded in a flexible optical circuit substrate with molded lenses
(or other light-guiding, fiber termination elements such as
mirrors, gratings, etc.) disposed at the ends of the fibers. The
lensed flexible optical circuit can be incorporated into a housing
to form any number of optical interconnect devices, such as optical
cassettes, optical multiplexers/demultiplexers, optical breakouts,
and optical monitoring stations. The lenses can be optically
interfaced to optical connectors (e.g., MPO, LC, ST, SC plugs) at
the ends of cables or at the interfaces of electro-optical devices
without the need for a full mating connector (e.g., MPO, LC, ST, SC
receptacles). Rather, a connector on an optical component, e.g., an
LC plug at the end of a fiber optic cable, can be plugged into an
adapter on a panel of the housing to optically couple to one of the
optical fibers on the flexible optical circuit inside of the
cassette enclosure via one of the lenses. The elimination of
conventional mating connectors inside the cassette significantly
reduces overall cost because it eliminates the skilled labor
normally associated with terminating an optical fiber to a
connector, including, polishing the end face of the fiber and
epoxying the fiber into the connector. It further allows the
optical interconnect device (e.g., an optical cassette) to be made
very thin. The housing for the lensed flexible optical circuit also
may be flexible. In yet other embodiments, there may be no housing
at all.
[0022] Since the lensed flexible optical circuit is mechanically
flexible, the concept of the present invention can be used in many
different applications, of which optical cassettes is merely one
example. For instance, it can be used to make right angle
connections. It may be curled into a cylinder and used to make
optical interconnections in existing conduit. The lensed flexible
optical circuit connectivity concept can be incorporated into
flexible housings, such as housings made of rubber so that a single
cassette can be used to make connections in different environments
and/or can compensate for offsets in all six degrees of freedom
(e.g., X, Y, Z, roll, pitch, and yaw).
[0023] The invention further can be incorporated into housings
having parts interconnected by one or more hinges so that the
housings are bendable about the hinges to provide similar
flexibility.
[0024] FIG. 3 show a top perspective view of such a lensed flexible
optical circuit 250 configured as an optical breakout circuit
incorporating the principles of the present invention.
Particularly, an optical fiber cable (not shown) on the right hand
side containing twelve fibers (e.g., six transmit fibers and six
receive fibers) is routed in pairs (one receive and one transmit)
to six, dual-fiber optical cables (not shown) on the left hand
side. Thus, the flexible optical circuit 250 includes twelve
optical fibers 217 routed accordingly. All of the embedded fibers
217 are terminated at each end to lens blocks 257 containing molded
lenses 230.
[0025] Considerable technology has been developed relating to the
design, fabrication, and use of such lenses in optical connectors,
which technology can be used to design and fabricate such lenses
230, terminate the optical fibers 217 with such lenses, and couple
light through such lenses to fibers in optical connectors. Such
information can be obtained from the following patents and patent
applications, all of which are incorporated herein fully by
reference. [0026] U.S. Pat. No. 7,722,261 entitled Expanded Beam
Connector; [0027] U.S. Patent Publication No. 2011/0096404 filed
Oct. 28, 2009 entitled Expanded Beam Interface Device and Method of
Fabricating Same; [0028] U.S. Patent Publication No. 2009/0097800
filed Oct. 9, 2008 entitled Multi-Fiber Ferrules for Making
Physical Contact and Method of Determining Same; [0029] U.S. Pat.
No. 6,208,779 entitled Optical Fiber Array Interconnection; [0030]
U.S. Pat. No. 6,480,661 entitled Optical ADD/DROP Filter and Method
of Making Same; [0031] U.S. Pat. No. 6,690,862 entitled Optical
Fiber Circuit; [0032] U.S. Pat. No. 6,012,852 entitled Expanded
Beam Fiber Optic Connector; and [0033] U.S. patent application Ser.
No. 12/836,067 filed Jul. 14, 2010 entitled Single-Lens,
Multi-Fiber Optical Connector Method and Apparatus.
[0034] More specifically, technology is available to couple a
connector directly in front of the lens 230 so that the lens does
not need to have its own conventional mating connector, such as
disclosed in aforementioned U.S. Pat. No. 7,722,261.
[0035] As shown in FIG. 4, such a lensed flexible optical circuit
250 may be disposed within a housing or other structure with
adaptors or other structure for receiving external connectors at
the ends of cables 105 or on other optical components so as to
optically couple with the lenses 230 without the need for a
conventional mating optical connector. For instance, FIG. 4 shows
the lensed flexible optical circuit 250 of FIG. 3 incorporated into
an optical cassette 200. Cables 103, 105 (or any other optical
components that are to be optically interconnected through the
lensed flexible optical circuit 250) may be terminated with
conventional connectors 107, 109. These connectors 107, 109 may be
plugged into adapters 115 on the cassette 200 adjacent the
respective lenses 230 and optically couple with the lenses 230
(and, through the lenses, with the fibers 217 of the flexible
optically circuit 250) without the need for a conventional,
complementary mating receptacle connector on the inside of the
cassette housing 201.
[0036] In yet other embodiments, such as illustrated in FIG. 5
(only the housing is shown), the entire housing 801 or at least the
side walls 803, 804, 805, 806 (i.e., the walls interconnecting the
panels 807 and 808 that bear the apertures 809, 810 that receive
the external connectors) may be made of a flexible material such as
rubber so that the housing 801 can be bent to accommodate
situations in which the optical components to be interconnected by
the device cannot be longitudinally aligned.
[0037] FIG. 6 illustrates yet a further embodiment in which the
lensed flexible optical circuit 901 includes a housing 900 that
comprises hinged members 902, 904. Specifically, the housing
comprises two housing pieces 902, 904 joined at a hinge 905 so that
the two housing pieces 902, 904 may be disposed relative to each
other at different angular orientations about the hinge 905. The
two lens blocks may be disposed on the opposing end faces 911, 912
of the housing 902. However, the illustrated embodiment shows a
more adaptable configuration that further includes an additional
panel 907 connected to housing piece 904 via a second hinge 908.
The lens block 909 is mounted on the panel 907, which can be
pivoted about hinge 908 to provide additional freedom in
positioning the ends of the flexible optical circuit relative to
each other.
[0038] Situations in which lensed flexible optical circuits are
useful are bountiful. For instance, because there are no internal
connectors (in lensed embodiments), the flexible optical circuit
interconnector can be made very thin. Particularly, it may comprise
a housing that, other than the end faces that receive the external
connectors, merely need be thick enough to house the flexible
optical circuit (and accommodate any necessary curvature thereof,
such as corrugations or an S curve as mentioned previously). In
fact, also as previously noted, in some embodiments, there may be
no housing at all and adapters or other structure for receiving the
external connectors may be incorporated directly on the flexible
optical circuit adjacent the end faces of the fibers and the
lenses. Accordingly, it can be used for very low profile
surface-mounted boxes, such as for use in low profile wall-mounted
interconnects for office buildings, etc. It also may be used for
interconnects in modular furniture pieces, which often provide very
small spaces for electrical or optical equipment.
[0039] Yet further, it is envisioned that a wide variety of optical
interconnects can be made modularly from a relatively small number
of modularly connectable housing components, flexible optical
circuits, lens blocks, and adapters. Particularly, there would need
to be a flexible optical circuit for each different optical routing
pattern type, e.g., 1 to 12 cable breakout (such as illustrated in
FIG. 3), shuffle (such as illustrated in FIGS. 1), 1 to 4 breakout,
1 to 4 optical splitter, etc. However, note that a single lensed
flexible optical circuit may be used for various different numbers
of breakouts, splits, shuffles, etc. For instance, a lensed
flexible optical circuit in accordance with the present invention
bearing fiber routing for ten 1 to 4 breakouts may be used to
create an optical cassette to provide anywhere from a single 1 to 4
breakout to as many as ten 1 to 4 breakouts. If the situation calls
for less than ten such breakouts, then some of the fibers/lenses
simply would not be used.
[0040] While the optical interconnects have been described herein
in connection with embodiments employing molded lenses, it will be
understood that this is merely exemplary and that other optical
components may be embedded in the laminate at the ends of the
fibers, such as diffraction gratings, Escalier gratings, mirrors,
and holograms.
[0041] Since the lensed flexible optical circuits are flexible,
they can be bent to accommodate many different physical layouts.
Furthermore, the lensed flexible optical circuits may be
constructed of sufficient length to accommodate longer
applications, but may be folded for shorter applications. In
cassette type or other application involving a housing, a set of
multiple housing pieces adapted to be modularly joined to each
other in various combinations may be provided. The housing
components may provide for hinged and/or fixed joining. One or more
of the housing components may be flexible. Thus, it is possible to
modularly create a wide variety of housing shapes, place one of the
flexible optical circuits within it and place lens blocks in
suitable adapters disposed in windows in the housings.
[0042] Since the lensed (FIG. 3) and unlensed (FIGS. 1 and 2)
flexible optical circuits discussed hereinabove contain optical
fibers, they can be bent too sharply so as to cause breakage of the
fibers or at least signal loss. Delamination of the flexible
optical circuit also is possible if bent too sharply. In order to
limit bending of the flexible optical circuits, a bend limiting
layer may be added to the laminate. FIG. 7 is a bottom perspective
view of a lensed flexible optical circuit 250 adapted to perform
the same functions as the 8-to-8 shuffle of FIGS. 1 and 2, except
employing a lensed flexible optical circuit such as in FIG. 3,
rather than an unlensed flexible optical circuit and conventional
internal connectors as in FIGS. 1 and 2. FIGS. 8A and 8B are
cross-sectional views through sections 8A-8A and 8B-8B,
respectively, in FIG. 7. In the illustrated embodiment, the bend
limiting layer 333 comprises a plurality of blocks 335 coupled to
each other via a flexible film 337. The blocks 335 are spaced from
each other and sized so that the layer 333 may freely bend to the
point at which the blocks 335 contact each other at their corners
in order to prevent further bending of the film, as illustrated in
region 340 in FIG. 9. More specifically, adjacent pairs of blocks
contact each other at their corners when a predetermined bend
radius is reached, thereby resisting further bending of the bend
limiting layer and, thereby, the flexible optical substrate to
which it is laminated. The bend limiting layer should be attached
to one of the major surfaces of the flexible optical circuit so as
to bend with and substantially identically to the flexible optical
circuit substrate, which can be achieved, for instance, by adhering
or otherwise attaching it to the flexible optical circuit substrate
substantially over the bend limiting layer's entire extent.
[0043] The spacing and size of the blocks should be selected so as
to prevent further flexing of the flexible optical circuit 250 when
the bend radius of the film is slightly less than the maximum
desired bend radius to prevent delamination, fiber breakage, and/or
signal loss within the fibers. The blocks may be hard or may have
some resilience in order to provide a soft bend limiting stop.
[0044] By providing a single, two-dimensional planar array of
blocks (e.g., rows and columns), bending is limited in two
directions, namely, the directions illustrated by arrow pairs A and
B in FIGS. 8A and 8B. More specifically, the spacing of the blocks
in direction X combined with the height of the blocks in dimension
Z collectively define the bend limit in direction A and the spacing
of the blocks in dimension Y combined with the height of the blocks
in the Z dimension collectively define the bend limit in direction
B. The blocks theoretically also can be used to limit bending
within the plane of the flexible optical circuit, but flexible
optical circuits generally are not sufficiently flexible in that
dimension to be of any concern.
[0045] If bend limiting is desired in only one direction, then the
plurality of blocks may comprise a single line of blocks (e.g., a
single row or column).
[0046] In the bend limiting layer 333 illustrated in FIGS. 7, 8A,
and 8B, the blocks 335 extend from the film 337 in only one
direction (downwardly from the film 337 in the Z dimension).
However, FIG. 10 shows an alternate embodiment of a bend limiting
layer that limits bending in both opposing directions about the
bend axis. Specifically, FIG. 10 is a cross-sectional side view
through an alternate embodiment of a bend limiting layer 333' in
which the blocks 335' extend from the film 337' in both directions
of the Z dimension, i.e., both above and below the plane defined by
the film 337'. This bend limiting layer 333' limits bending in both
directions about the bend axis (see arrow pairs C and D). If
desired for any reason, the bend limit in the two directions of
each arrow pair can be made different by making the blocks
asymmetric about the plane defined by the film 337 (i.e., having a
different height above the plane of the film 337 than below the
film). In fact, since the bend limiting layer 333 is placed on one
side of the flexible optical circuit 250, the blocks 335 actually
would need to be slightly different heights above and below the
film 337 in order to provide identical bend limits in both arrow
pair directions because the film would stretch when bent in one
direction and compress in the other direction. In other
embodiments, instead of a single block extending through the film
in both directions, different blocks may be disposed on one side of
the film than on the other side.
[0047] Yet further, the blocks 335 can be disposed on one side of
the film 337 so as to limit bending only in one direction of the
arrow pair A and/or arrow pair B. In some embodiments, a first bend
limiting layer may be disposed on one side of the flexible optical
circuit and a second bend limiting layer may be disposed on the
other side of the flexible optical circuit substrate in order to
collectively provide bend limiting in both directions of the arrow
pair(s).
[0048] The blocks need not be uniformly spaced. For example, if for
any reason it is desired to allow a first portion of the flexible
optical circuit to bend more than a second portion, the blocks may
be spaced further apart (and/or made shorter) in the first portion
of the bend limiting layer than in the second portion. Furthermore,
the bend limit in the two orthogonal directions represented by
arrow pair A on the one hand and arrow pair B on the other hand
need not necessarily be equal. For example, the blocks may be
spaced at longer intervals in dimension Y than in dimension X so as
to allow greater bending (i.e., bending to a smaller radius) in the
direction of arrow pair B than in the direction of arrow pair A.
The particular routing of the fibers on the flexible optical
circuit very well may dictate the ability to allow much greater
bending in one direction or one portion of the flexible optical
circuit than in another. For instance, the flexible optical circuit
of FIGS. 3, 4, 5A, and 5B, in which the fibers run substantially in
the X dimension, can be allowed to bend to a much smaller radius in
the direction of arrow pair B (i.e., bending about an axis
substantially parallel to the fibers) than in the direction of
arrow pair A (i.e., bending about an axis substantially
perpendicular to the fibers). This feature could be very important
in flexible optical circuits that need to be rolled into a
cylinder, such as to fit within existing conduit.
[0049] Yet further, while the blocks 335 are substantially cubic in
the illustrated embodiments, this is merely exemplary. The blocks
may be of essentially any shape, such as cubes, cylinders,
semi-cylinders, sphere, hemispheres, rectangular prisms, triangular
prisms, truncated cones (frustums), truncated pyramids, etc. In
fact, the shape, and not merely the size, of the blocks may be used
to dictate the bend limit in different directions. In addition, the
shapes of the blocks may be different in different portions of the
flexible optical circuit substrate so as to provide different bend
limits in different portions of the flexible optical circuit
substrate.
[0050] The film layer 337 preferably is formed of a flexible and
resilient film, such as another layer of Mylar (a trademark of E.I.
DuPont De Nemours and Company) or another flexible and resilient
polymer. The film preferably is resilient because it may need to
stretch and compress so as not to delaminate from the flexible
optical circuit during bending and/or so as not to unnecessarily
resist bending in the direction opposite of the side of the
flexible optical circuit on which it is disposed.
[0051] The blocks 335 may be either embedded in the film 337, as
illustrated, or adhered to one side of the film. In other
embodiments, the bend limiting layer 333 may be of unitary
construction, such as a molded piece made of a single material such
as Mylar.TM. with the block portions 335 simply being molded
thicker than the intermediate, film portions 337. Alternately, the
blocks may be formed of any reasonable hard or semi-hard material,
such as polyethylene, hard rubber, metal, etc.
[0052] In yet other embodiments, the blocks 335 need not be
attached to a separate film such as film 337, but instead may be
adhered to or otherwise disposed directly on one or both of the
opposing major surfaces 338, 339 of the flexible optical circuit
250 itself.
[0053] In embodiments in which the flexible optical circuit 250 is
disposed within a bendable housing such that the flexible optical
circuit only bends essentially as dictated by the bending of the
housing, such as in the embodiments illustrated in FIGS. 7 and 8,
then the bend limiting layer(s) may be applied to the housing
instead of the flexible optical circuit. FIG. 11 illustrated such
an embodiment. In this embodiment, two bend limiting layers 350,
352 are disposed on opposite sides 803, 805 of the flexible housing
801 of FIG. 9.
[0054] Having thus described particular embodiments of the
invention, various alterations, modifications, and improvements
will readily occur to those skilled in the art. Such alterations,
modifications, and improvements as are made obvious by this
disclosure are intended to be part of this description though not
expressly stated herein, and are intended to be within the spirit
and scope of the invention. Accordingly, the foregoing description
is by way of example only, and not limiting. The invention is
limited only as defined in the following claims and equivalents
thereto.
* * * * *